The feeling, like the term "schwa (the phonetic term to describe the "dead vowel" that native English speakers use instead of a definitive vowel), describing an event that was neither good, nor bad, exciting nor dull, etc. It is used mostly when answering the question, "How was your day?". People who are sick and tired of just the reply "good" will use, or ask others to use this instead.

"How was your day?"
"Schwaggy"

"How was your midterm exam?"
"Schwaggy"

"What provoked you to make the term 'Schwaggy'?"
"Linguistics at TWU..."